<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
</head>
<body>
<h1>0</h1>
<script>
    let count=0;
    setInterval(f,1000);
    function f() {
        count++;
        let h1=document.querySelector("h1");
        h1.innerText=count;
        if(count==5){
            clearInterval(timer);
        }
    }
    setInterval(function () {
        console.log(count);
    },1000);
    setTimeout(function (){
        alert(location.href);
        location.href="http://www.baidu.com"
    },3000);
</script>
</body>
</html>